Generally, binders are useful in fabricating articles because they are capable of consolidating non- or loosely-assembled matter. For example, binders enable two or more surfaces to become united. In particular, binders may be used to produce products comprising consolidated fibers. Thermosetting binders may be characterized by being transformed into insoluble and infusible materials by means of either heat or catalytic action. Examples of a thermosetting binder include a variety of phenol-aldehyde, urea-aldehyde, melamine-aldehyde, and other condensation-polymerization materials like furane and polyurethane resins. Binder compositions containing phenol-aldehyde, resorcinol-aldehyde, phenol/aldehyde/urea, phenol/melamine/aldehyde, and the like are widely used for the bonding of fibers, textiles, plastics, rubbers, and many other materials.
The mineral wool and wood board industries have historically used a phenol formaldehyde based binder, generally extended with urea. Phenol formaldehyde type binders provide suitable properties to the final products; however, desires for greater sustainability and environmental considerations have motivated the development of alternative binders. One such alternative binder is a carbohydrate based binder derived from reacting a carbohydrate and an acid, for example, U.S. Published Application No. 2007/0027283 and Published PCT Application WO2009/019235. Another alternative binder is the esterification products of reacting a polycarboxylic acid and a polyol, for example, U.S. Published Application No. 2005/0202224. Because these binders do not utilize formaldehyde as a reagent, they have been collectively referred to as formaldehyde-free binders.
One area of current development is to find a replacement for the phenol formaldehyde type binders across a large range of products, including products in the building and automotive sector (e.g. mineral wool insulation, wood boards, particle boards, plywood, office panels, and acoustical sound insulation). In particular, previously developed formaldehyde-free binders may not possess all of the desired properties. For example, acrylic acid and poly(vinylalcohol) based binders have shown promising performance characteristics for some (but not all) products. However, these are relatively more expensive than phenol formaldehyde binders, are derived essentially from petroleum-based resources, and have a tendency to exhibit lower reaction rates compared to the phenol formaldehyde based binder compositions (requiring either prolonged cure times or increased cure temperatures).
Carbohydrate-based binder compositions are made of relatively inexpensive precursors and are derived mainly from renewable resources. However, these binders may also require reaction conditions for curing that are substantially different from those conditions under which the traditional phenol formaldehyde binder system is cured.
Specifically, a versatile alternative to the above-mentioned phenol formaldehyde binders is the use of carbohydrate polyamine binders which are polymeric binders obtained by reaction of carbohydrates with polyamines having at least one primary amine group. These carbohydrate polyamine binders are effective substitutes for phenol formaldehyde binders, since they possess similar or superior binding characteristics and are highly compatible to the established processes.
Typically, the carbohydrate polyamine binders are prepared as a solution, such as an aqueous solution, and are subsequently applied onto the loosely assembled matter to be bound. The such wetted loosely assembled matter is then, for example, heat treated to cure the carbohydrate polyamine binder.
Nonetheless, the rather high concentration of solids in the carbohydrate polyamine binder solution is connected to a variety of disadvantages, such as quick gelling or solidification of the binder solution, as well as recrystallization of the carbohydrate component. Based on the rather short shelf-life, further problems regarding storage and shipment of the carbohydrate polyamine binders are observed.
Accordingly, the technical problem underlying the present invention is to provide improved binders, particularly binders which are compatible with the established processes, are environmentally acceptable and overcome the aforementioned problems.